In bar-wound electric motor assemblies, wires are typically welded together to assemble a stator. Quality welds are necessary because if one weld fails the motor fails. Because hundreds of welds may be required for a single motor, it is important that the welding process be highly robust and efficient so as to assure weld quality while minimizing the welding process time. Problems with current welding methods include the lack of quality welds due to misaligned wires and inefficient processes that have been introduced to align wires or increase the robustness of welds.
The free ends of wires typically require some alignment assistance in preparation for the welding process. For example, a robot end effecter (fingers) is used to hold a wire pair together. Two fingers are used to locate each pair of wires. A finger is inserted from each side of the pairs and then the two fingers are closed together to bring the two wires adjacent to each other in the perimeter direction. In addition, the fingers are designed to bring the two wires adjacent in the radial direction with the fingers holding the wires against each other. When the pair of wires is restrained in both directions by the fingers, the welding takes place and the fingers release the wires and retract out of the stator. Then, the stator indexes to the next slot to weld another pair of wires. This process is tedious and problems occur. For example, if the indexing and the wire bend do not lineup, the fingers hit the wires while being inserted into the stator.
In sum, without precisely aligning the pair of wires, the resulting weld could be defective. However, the robot end effector and other complex wire positioning tooling that has been introduced to align wire pairs prior to welding is expensive and complex. Therefore, there is a need for a joining method for reliably and reproducibly joining wires together.